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Therapeutics > anaesthetics > Flashcards

anaesthetics Flashcards

1
Q

what category of medicine is a topical anaesthetic

A

POM (prescription only medicine)

so only healthcare professionals have access to them

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2
Q

topical anaesthetics are drugs that ____________ block ________________ in ____________ nerves

A

topical anaesthetics are drugs that reversibly block transmission in sensory nerves

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3
Q

list 5 indications for use of a topical anaesthetic

A
  • contact tonometry
  • contact lens fitting
  • foreign body removal
  • gonioscopy
  • lacrimal procedures
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4
Q

what indication will you never use a topical anaesthetic for

A

the relief of symptoms

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5
Q

what type of contact lens fitting will you use a topical anaesthetic

A

if your going to make an impression of the eye e.g. for scleral lenses

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6
Q

what does topical anaesthetics delay

A

corneal epithelial cell healing, so it is not good for a patient with corneal abrasions

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7
Q

list 3 advantages of topical anaesthetics

A
  • allows certain procedures to be conducted
  • makes the patient more comfortable
  • makes procedures easier for the practitioner
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8
Q

list 4 disadvantages of topical anaesthetics

A
  • stings (due to pH)
  • delays healing
  • eye is more susceptible to damage (due to delayed healing, it is more compromised)
  • repeated installations
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9
Q

the most mode action of topical anaesthetic

  • _________ information passes along _______ _______ __________ _________ (action potentials)
  • nerve has __________ charge at _______
  • _______ ________ is generated in _______ of _________ ions into the ________ and this results in a _________ charge (depolarisation)
  • efflux of __________ ions returns the nerve to _________ potential causing _______________
  • the action potential passes along the nerve along with _____________ ___________ and depolarisations of ________ areas
  • topical anaesthetics __________ block nerve conduction
  • they block ___________ channels therefore action potentials ______ be generated
A
  • sensory information passes along nerve fibres electrical impulses (action potentials)
  • nerve has negative charge at rest
  • action potential is generated in influx of sodium ions into the nerve and this results in a positive charge (depolarisation)
  • efflux of potassium ions returns the nerve to resting potential causing repolarisation
  • the action potential passes along the nerve along with successive depolarisations and depolarisations of adjacent areas
  • topical anaesthetics reversibly block nerve conduction
  • they block sodium channels therefore action potential can’t be generated
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10
Q

which topical anaesthetic stings the most

A

amethocaine (tetracaine)

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11
Q

what is the onset and duration of amethocaine

A

onset 1 min

duration 20 min

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12
Q

what is the onset and duration of benoxinate

A

onset 1 minute

duration 15 minutes

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13
Q

what is the onset and duration of proxymetacaine

A

onset 1 minute

duration 15 minutes

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14
Q

what is the onset and duration of lignocaine

A

onset 1 minute

duration 30 minutes

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15
Q

what is another name for amethocaine

A

tetracaine

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16
Q

what is another name for benoxinate

A

oxybuprocaine

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17
Q

what is another name for proxymetacaine

A

proparacaine

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18
Q

what is another name for lignocaine

A

lidocaine

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19
Q

which topical anaesthetic has the longest duration

A

lignocaine

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20
Q

what are the 2 types of possible chemical structures of topical anaesthetics

A
  • ester link
    or
  • amide link
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21
Q

which chemical structure of topical anaesthetic is more linked to allergic reactions

A

ester link

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22
Q

what is the ester link chemical structure hydrolysed by

A

cholinesterase

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23
Q

what is the amide link resistant to

A

hydrolysation

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24
Q

which chemical structure has a longer duration

A

amide link

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25
Q

list the 3 ester link topical anaesthetics

A
  • oxybuprocaine
  • tatracaine
  • proparacaine
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26
Q

what is the amide link topical anaesthetic

A

lignocaine

27
Q

what portions/parts do all of the topical anaesthetics have

A

lipophilic (insoluble) and hydrophilic (soluble) parts that are linked together either by an ester link or an amide link

28
Q

which chemical strict of topical anaesthetic is broken down more easily

A

ester linkage

29
Q

which topical anaesthetic is the most potent and provides the deepest anaesthesia and what does this make it good for

A

tertacaine (amethocaine)

makes it good for foreign body removal

30
Q

sensitivity of tetracaine/amethocaine is _________ and occurs after ____________ _________

A

sensitivity of tetracaine/amethocaine is rare and occurs after repeated doses

31
Q

what is tetracaine/amethocaine associated with

A

punctate staining

32
Q

list the 4 contraindications/cautions of tetracaine/amethocaine

A
  • sulphonamides
  • premature babies
  • known allergy
  • pregnancy/lactation
33
Q

what form of packaging and what doses is tetracaine/amehocaine available in and what are the storage conditions

A
  • 0.5% and 1.0%
  • minims
  • protect from light (a cupboard stops it from destabilising)
34
Q

what may happen if tetracaine/amethocaine is not protected from light

A

it will be hydrolysed by the light, causing it to destabilise

35
Q

how can tetracaine/amethocaine damage the cornea

A

if the solution dose is over 1% concentration

36
Q

what is it possible to do after just one drop of tetracaine/amethocaine

A

removal or foreign body

37
Q

which topical anaesthetic is the most widely used by optometrists in the UK

A

oxybuprocaine/benoxinate

38
Q

how likely are sensitivity reactions with oxybuprocaine/benoxinate

A

rare

39
Q

what does oxybuprocaine/benoxinate have less of that tetracaine/amethocaine

A

less stinging, irritation

40
Q

what special property does oxybuprocaine/benoxinate have and how can this also be a disadvantage

A

bactericidal properties

but when want to take a swab of the eye to test for bacteria it produces false results as it has killed some of it off

41
Q

list the 4 contraindications/cautions of oxybuprocaine/benoxinate

A
  • known allergy
  • if other eyedrops containing chlorhexidine acetate as a preservative are being used
  • pregnancy/lactation
  • premature babies
42
Q

what form of packaging and dose is oxybuprocaine/benoxinate available in and what is the storage conditions

A
  • 0.4%
  • minims
  • store below 25 degrees celsius and protect from light
43
Q

how can oxybuprocaine/benoxinate be used in ophthalmology

A
  • three drops are instilled over a five minute interval which allows foreign body to be removed
  • corneal sensation recovers after one hour
44
Q

which topical anaesthetic stings the least

A

proxymetacaine/proparacaine

45
Q

proxymetacaine/proparacaine causes the minimal __________ ___________ __________, ideal for ___________

A

proxymetacaine/proparacaine causes the minimal punctate corneal staining, ideal for tonometry

46
Q

why is proxymetacaine/proparacaine used in hospitals more and what is it useful for

A

because it has the least antibacterial properties, useful when taking conjunctival swabs

47
Q

list the 5 contraindications/cautions with proxymetacaine/proparacaine

A
  • known allergy
  • overactive thyroid
  • heart disease
  • premature babies
  • pregnancy/lactation
48
Q

how common is sensitivity with proxymetacaine/proparacaine

A

rare

49
Q

what form of packaging and dose is proxymetacaine/proparacaine available in and what are the storage conditions

A
  • 0.5%
  • minims
  • store between 2-8 degrees celsius - has to be kept in a refrigerator
50
Q

what type of surgery can proxymetacaine/proparacaine be used in and how is it used in this condition

A

cataract extraction
1 drop every 5 - 10 minutes
5 - 7 drops in total

51
Q

which other topical anaesthetic does lidocaine/lignocaine sting less that

A

tetracaine/amethocaine

52
Q

when is lidocaine/lignocaine used

A

when a patient is sensitive to the ester link

53
Q

what are the contraindications/cautions with lidocaine/lignocaine

A
  • pregnancy/lactation

- premature babies

54
Q

why is lidocaine/lignocaine good for goldmann tonometry

A

because it comes combined with fluorescein

55
Q

what form of packaging and dose does lidocaine/lignocaine come in and what are the storage conditions

A
  • 4% minims combined with 0.25% flourescein
  • minims
  • store below 25 degrees celsius and protect from light
56
Q

what dosage of fluorescein does lidocaine/lignocaine come with

A

0.25%

57
Q

list 6 possible side effects that can occur with any topical anaesthetic from least to most worse

A
  • transient stinging
  • transient blurring
  • conjunctival hyperaemia
  • mild superficial epithelial damage, especially with stronger drops such as tetracaine which represents local toxicity
  • punctate keratitis
  • hypersensitivity reactions (less likely with lidocaine), range from mild transient blepharoconjunctivitis to diffuse necrotising epithelial keratitis
58
Q

what is the incidence of necrotising keratitis incidence with ester drugs

A

1/1000

59
Q

repeated use can lead to __________ ____________ can lead to _______________ _______________

A

repeated use can lead to epithelial toxicity can lead to serious keratopathy

60
Q

what 4 things can serious keratopathy lead to

A
  • epithelial loss
  • stromal oedema
  • corneal infiltrates
  • anterior chamber reaction
61
Q

what must you instruct to your patient in regards to topical anaesthetics

A

not to rub the eyes

cannot leave practice until anaesthetic had worn off

62
Q

what is increased by instillation of topical anaesthetic

A

permeability of epithelium cells thus enhances effect of other drugs e.g. when using in combination with cyclopentolate in dark eyes

63
Q

what is reduced by topical anaesthetics

A

healing of epithelial cells

64
Q

who is topical anaesthetics open to abuse by

A

health care practitioners

Therapeutics (19 decks)

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